Pellets with solar thermal or photovoltaic?

The heating capacity is currently only an estimate. An exact calculation will follow. It is also not yet decided which rooms in the basement will be heated. The 175 sqm are calculated without the basement.

We have just under 220m² of heated space as KFW55 and a heat demand of 18.9 kWh/m². Even with hot water, you are far from 12 kW. In terms of costs, pellet heating is certainly the most expensive way to heat in a KFW new build. And the ST is only a means to an end for gas new builds; otherwise, no one does that voluntarily.

I would not make pellets, in my opinion the horse is dead.

Photovoltaics also work in winter, even with clouds and fog. ST actually only works if you don’t need it anyway, except for a bit of hot water - which fits well with your chosen heating system.

A 12 kW heating system in a 175 sqm KFW55 house is already gross nonsense. A pellet heating system is also quite questionable in new buildings - why? Solar thermal is only done with gas (to be allowed to build it) - it is not worthwhile.

I think once Ziegenpeter has been given the exact energy calculation as well as the costs for the Schmarrnn, the matter will be off the table anyway.

I consider 12 kW to be quite large for a new building - but how "small" can pellets actually be? When it burns, it burns, right? I guess such heating systems are built with a large buffer tank anyway, so that you can actually use the fairly high heat sensibly without cycling 20 times a day. But I’m not a heating engineer...

Regarding heat pumps and crystal balls: At some point, all the forests will have been cleared through Eastern European overexploitation (and not replanted), or the governments of those countries will find an effective measure against it. And by then at the latest, pellets will become even more expensive and heat pumps will become interesting again. The fact that, due to the new subsidies, probably a high percentage of all old buildings will switch to pellets doesn’t make it any better.

But with a well-designed underfloor heating system, the renovation costs are quite manageable. Or my crystal ball is cracked anyway, then you can safely discard this whole post.